Apparatus which detects lines approximating an image by repeatedly narrowing an area of the image to be analyzed and increasing the resolution in the analyzed area

An apparatus for detecting a rectilinear line of an object comprising:

• generating means for inputting an analog picture image of said object and generating image data which represents said picture image of said object in an X and Y orthogonal coordinate system;
• determining means for determining a plurality of feature points (Xs, Ys), wherein said plurality of feature points (Xs, Ys) are defined by values and distributions of said image data on said picture image and wherein at least some of said plurality of feature points (Xs, Ys) correspond to said rectilinear line;
• first converting means for respectively converting each of said plurality of feature points (Xs, Ys) into corresponding first groups of points (r1, t1), wherein said corresponding first groups of points (r1, t1) respectively represent curves in a first r1-t1 polar coordinate system having a first resolution and a first range;
• first memory means for storing first frequency data, wherein addresses of said first memory means respectively relate to points of said first r1-t1 polar coordinate system;
• first incrementing means for incrementing said first frequency data, wherein said first incrementing means increments said first frequency data stored at a first certain address of said first memory means for each instance that one point in one of said corresponding first groups of points (r1, t1) relates to said first certain address;
• first selecting means for selecting a first particular point (rm1, tm1) in said first r1-t1 polar coordinate system, wherein said first particular point (rm1, tm1) corresponds to a first particular address of said first memory means at which said first frequency data represents a maximum value;
• second converting means for respectively converting at least some of said plurality of feature points (Xs, Ys) into corresponding second groups of points (r2, t2), wherein said corresponding second groups of points (r2, t2) respectively represent curves in a second r2-t2 polar coordinate system having a second resolution and a second range, wherein said second r2-t2 polar coordinate system is centered about said first particular point (rm1, tm1), and wherein said second resolution is higher than said first resolution and said second range is narrower than said first range;
• second memory means for storing second frequency data, wherein addresses of said second memory means respectively relate to points of said second r2-t2 polar coordinate system;
• second incrementing means for incrementing said second frequency data, wherein said second incrementing means increments said second frequency data stored at a second certain address of said second memory means for each instance that one point in one of said corresponding second groups of points (r2, t2) relates to said second certain address;
• second selecting means for selecting a second particular point (rm2, tm2) in said second r2-t2 polar coordinate system, wherein said second particular point (rm2, tm2) corresponds to a second particular address of said second memory means at which said second frequency data represents a maximum value;
• and
• line determining means for determining said rectilinear line in said X and Y orthogonal coordinate system, wherein said rectilinear line is based at least partially on said second particular point (rm2, tm2) and approximates a succession of at least some of said plurality of feature points (Xs, Ys).